There are many cases where a plurality of 2-lamp fluorescent lamp appliances are installed on the ceilings in offices, stores, factories, and the like to illuminate the whole interior. As such 2-lamp fluorescent lamp appliances, there are a serial-type appliance and a parallel-type appliance, but the serial-type appliances are put into wide use as illumination equipment from the viewpoint of excellent performance and price, and the parallel-type appliances, which can be easily controlled to be turned on and off, are widely employed as signboards such as outdoor billboards (Patent Literature No. 1 & No. 2).
Recently, energy saving is required, regarding illumination, when bright illumination using 2 lamps is not necessary, such as during daylight, one lamp is turned off to save electric power. However, in the serial-type 2-lamp fluorescent lamp appliances, when one lamp is taken off, the other lamp is also turned off.
Thus, in the 2-lamp serial-type fluorescent lamp appliances, a method is proposed in which a dummy tube connected to current-carrying means with a small direct-current resistance is connected between two opposed connection terminals, instead of a general fluorescent lamp, and the one remaining lamp is turned on (Patent Literature No. 3, No. 4 & No. 5). In these 2-lamp serial-type fluorescent lamp appliances, the dummy tube is used, and thus the dummy tube has to be replaced with a general fluorescent lamp when bright illumination is needed, such as at nighttime, which requires a complicated operation.
A fluorescent lamp appliance is proposed in which the number of ON/OFF operation times of a power supply switch provided on the wall is counted, and an operation of a bimetal-type starter of a fluorescent lamp is permitted or prevented according to the number of operation times (Patent Literature No. 6).
Meanwhile, the inventor of the present invention developed a fluorescent lamp appliance and applied for a patent, in which a current-carrying circuit of one fluorescent lamp in a 2-lamp parallel-type fluorescent lamp is provided with switching means and the switching means is closed or opened by a control circuit including a D-type flip-flop circuit operating according to the ON/OFF operation of a power supply switch (Patent Literature No. 7). In the fluorescent lamp appliances, it is possible to turn on only one lamp as necessary by the operation of the power supply switch, it is possible to save electric power by turning off one lamp in the daytime or the like, and it is possible to secure bright illumination by turning on two lamps at nighttime or the like.